Human migration (derived from Latin: migratio) is physical movement by humans from one area to another, sometimes over long distances or in large groups. Historically this movement was nomadic, often causing significant conflict with the indigenous population and their displacement or cultural assimilation. Only a few nomadic people have retained this form of lifestyle in modern times. Migration has continued under the form of both voluntary migration within one's region, country, or beyond and involuntary migration (which includes the slave trade, trafficking in human beings and ethnic cleansing). People who migrate into a territory are called immigrants, while at the departure point they are called emigrants. Small populations migrating to develop a territory considered void of settlement depending on historical setting, circumstances and perspective are referred to as settlers or colonists, while populations displaced by immigration and colonization are called refugees. The rest of this article will cover sense of a "change of residence", rather than the temporary migrations of travel, tourism, pilgrimages, or the commute.

Spencer Wells (born April 6, 1969 in Georgia, United States) is a geneticist and anthropologist, an Explorer-in-Residence at the National Geographic Society, and Frank H.T. Rhodes Class of '56 Professor at Cornell University. He leads The Genographic Project.

Wells grew up in Lubbock, Texas. He obtained a Bachelor of Science in Biology from the University of Texas at Austin in 1988, and a Ph.D. in Biology from Harvard University in 1994. He was a postdoctoral fellow at Stanford University between 1994 and 1998, and a research fellow at Oxford University between 1999 and 2000.

Wells did his Ph.D. work under Richard Lewontin, and later did postdoctoral research with Luigi Luca Cavalli-Sforza and Sir Walter Bodmer. His work, which has helped to establish the critical role played by Central Asia in the peopling of the world, has been published in journals such as Science, American Journal of Human Genetics, and the Proceedings of the National Academy of Sciences.

He wrote the book The Journey of Man: A Genetic Odyssey (2002), which explains how genetic data has been used to trace human migrations over the past 50,000 years, when modern humans first migrated outside of Africa. According to Wells, one group took a southern route and populated southern India and southeast Asia, then Australia. The other group, accounting for 90% of the world's non-African population (some 5 billion people as of late 2006), took a northern route, eventually peopling most of Eurasia (largely displacing the aboriginals in southern India, Sri Lanka and Southeast Asia in the process), North Africa and the Americas. Wells also wrote and presented the PBS/National Geographic documentary of the same name. By analyzing DNA from people in all regions of the world, Wells has concluded that all humans alive today are descended from a single man who lived in Africa around 60,000 - 90,000 years ago, a man also known as Y-chromosomal Adam.